A USB operation is performed by a USB device and a USB host. The USB device, which provides its function to the USB host, serves as a server, and the USB host operates as a client which controls the USB device and requests the function of the USB device.
A remote USB technique, which virtually performs the functions of the USB device and USB host, enables a remotely existing USB device to operate in the same manner as that of a local USB device through a network. A remote USB device server connected through a network is recognized by an upper user program and an operating system (OS) like the USB device connected to a local USB connection terminal does. Therefore, the remote USB device server and the remote USB host are connected through a network and virtualized each other so as to operate. In this manner, the conventional remote USB technique allows a USB device not attached to a local host to be virtualized as a USB device attached to the local host so as to operate. Its application to a virtualization system server driving a virtual machine allows for a virtual USB virtualizing a remote USB device as a USB device of a virtual machine.
However, when the virtual machine live-migrates from one physical host to another physical host for the reason of load balancing or the like, a connection from the virtual USB is cut off, potentially stopping a data transmission, or the like performed by the virtual USB to lose data. Thus, a virtual machine is restricted in using the virtual USB of the virtual machine due to the live migration of the virtual machine, and due to this problem, the live migration of the virtual machine according to a network environment, a load state of a server, a failure recovery, and the like is not supported when a manager of a server pool that drives the virtual machine uses the virtual USB. Namely, a management of resources of the server driving the virtual machine is restricted.